Fixed-die floorplanning is an important problem in the modern physical design process. An effective floorplanning algorithm is crucial to improving both the quality and the timeto-market of the design. In this paper, we present an analytical floorplanning algorithm that can be used to efficiently pack soft modules into a fixed die. The locations and sizing of the modules are simultaneously optimized so that a minimum total wire length is achieved. Experiments on the MCNC and GSRC benchmarks show that our algorithm can achieve above a 90% success rate with a 10% white space constraint in the fixed die, and the efficiency is much higher than that of the simulated annealing based algorithms for benchmarks containing a large number of modules.